Power quality

Learn more about the various factors that influence power quality, about power quality standards and about how power quality is assessed.

Our transmission system meets the quality and reliability standards of the Northeast Power Coordinating Council (NPCC),
which regulates transmission providers in northeastern North America and has some of the most stringent criteria on the continent.

Our distribution system supplies power at voltages within the limits recommended in CSA
Standard CAN3-C235-83 for low- and medium-voltage power systems.

If you find that your supply voltage is outside normal limits (for example, not between 110 V and 125 V for a 120-V supply), contact
Customer Services at 1 -800 -790-2424 or your commercial delegate.

Standards and characteristics

Voltage limits at the connection point of deliveryAs specified in CAN3-C235-83

Normal operating conditions

Minimum (volts)

Maximum (volts)

Single-phase120/240 V

110/220

125/250

3-phase
quadruplex
120/208 V

112/194

125/216

3-phase
quadruplex
347/600 V

318/550

360/625

3-phase
triplex
600 V

550

625

Extreme operating conditions

Minimum (volts)

Maximum (volts)

Single-phase120/240 V

106/212

127/254

3-phase
quadruplex
120/208 V

110/190

127/220

3-phase
quadruplex
347/600 V

306/530

367/635

3-phase
triplex
600 V

530

635

Note: If the voltage remains within the limits for normal operating conditions, no improvements or corrective action are necessary. If it remains within the range for extreme operating conditions, improvements or corrective action should be planned according to a definite schedule but not necessarily on an emergency basis. If the voltage is outside these limits, Hydro-Québec must take urgent action to remedy the situation.

Voltage disturbances

Power disturbances are waveform distortions that are very often due to the use of high-power electrical equipment, which affects the grid when in use. It can affect the operation of other equipment depending on how sensitive it is and on the degree of waveform distortion.

It is possible to correct the problem and improve the electromagnetic compatibility of your equipment with the supply voltage; however, solutions must be assessed on a case-by-case basis by a specialist (master electrician or engineer), who should factor in the cost and the impact on your company’s productivity.

Indoors

Outdoors

Escalators and passenger/freight elevators

Air conditioners

Fluorescent lights

Vending machines

Variable-frequency drive motors

Photocopiers

Welding machines

Telephone switching systems

Fans

Arc or induction furnaces

Accidents

Tree limbs in contact with lines

Lightning

Air pollution

Magnetic storms

Strong winds

Electromagnetic Compatibility

Electromagnetic compatibility is the ability of equipment to function satisfactorily in its electromagnetic environment without introducing intolerable disturbances to anything in that environment.

Under the Conditions of Electricity Service [PDF],
your electrical installation must be designed, built, connected, protected, used and maintained in such a way that it does not cause disturbances on the power system.
Disturbances can be caused by a number of phenomena: voltage and current fluctuations, flicker, harmonics, etc.
In order to maintain power quality, Hydro-Québec must ensure that the various types of disturbances do not exceed the thresholds on its power system.
If necessary, Hydro-Québec will ask you to conduct the appropriate studies. For example, standards
C.22-03 [PDF] (in French only) and C.25-01 [PDF] (in French only) contain specific requirements regarding flicker and harmonics. It should also be noted that large, disturbance-causing equipment (welding machines, variable-frequency drives, power electronics, etc.) can be incompatible with sensitive equipment and can cause the allowable disturbance thresholds to be exceeded.

Hydro-Québec encourages you to look for equipment that meets the Canadian standards for immunity to disturbances
.
Equipment with electronic components is highly sensitive to power disturbances. Electromagnetic incompatibility between your equipment and the voltage delivered by Hydro-Québec can lead to damage or malfunction and can even shorten the service life of your equipment.

Filters placed in series at the entrance to a variable-frequency drive can improve immunity against transient surges on the power grid.

It is your responsibility to guard against the consequences of a power loss, particularly on just one phase, whether or not your equipment is protected by fuses.

Benefit from our evaluation and technical studies services

Hydro-Québec provides you with the technical support of its experts. The services described below will help you to identify voltage quality-related problems and to take any necessary corrective measures.

Signature service: expert analysis and diagnosis of power quality, which includes the installation of a measurement tool designed for real-time data capture. The results of the analysis of this data helps customers avoid recurring production losses.

Questions about power quality?

This document describes the main characteristics of the voltage supplied by the Hydro-Québec distribution system.
It lists the various phenomena that influence power quality and proposes measures for protecting your equipment and reducing the potential impacts of disturbances.